With container mounted manual pump dispensers, it is now common to use gas-producing substances, for example, hydrogen peroxide which generates gas when it comes in contact with water containing iron. The stress produced by such positive pressure can result in deformation of the container, cracking, leakage and so on. The problem is particularly acute where, in order to reduce cost or environmental impact, thinner-walled containers are used.
U.S. Pat. No. 5,752,629 to Michael E. Hardy issued May 19, 1998 deals with the need for passive means to vent gas buildup in containers having pump dispensers attached. Specifically, the Hardy patent provides gas-permeable material preferably in a frame over an opening in the container cap provided in the pump dispenser.
While in the past mechanical means have been used to permit venting of the outside air into the container, such venting means are usually only open upon the actuation of the trigger, for instance. Such mechanical means would also vent built-up gas pressure to the outside. However, during periods of storage the trigger is never actuated and, hence, the mechanical means does not operate to permit venting of built-up gases to the outside.
It is an object of the present invention to provide in a pump dispenser passive means--as opposed to mechanical means--for venting built-up gases from the container without appreciably altering the structure of the pump and without permitting leakage of liquid product if the container tips over.